Why doesn't Nougat show data usage per app?

[AC Question]

I recently bought a new phone and it's Nougat. I used to use a Jellybean and it used to show me which app was using how much data. But now this Nougat version isn't showing that. I downloaded an app just for this reason but it sees only Android OS as the data user. I go and watch a video and the app says the OS just used 20 mb of data. And while WiFi usage for per app is enabled in the settings, I can't see it for the cellular network.
I don't understand. It doesn't feel like an update to me. I mean why did they take this feature away?